Gas turbine engines, such as turbofan gas turbine engines, may be used to power various types of vehicles and systems, such as, for example, aircraft. Typically, these engines include turbine blades (or airfoils) that are impinged by high-energy compressed air that causes a turbine of the engine to rotate at a high speed. Consequently, the blades are subjected to high heat and stress loadings which, over time, may reduce their structural integrity.
Modern aircraft jet engines have employed internal cooling systems in the blades to maintain the blade temperatures within acceptable limits. Typically, the blades are air cooled using, for example, bleed air from a compressor section of the engine. The air may enter near the blade root, and then flow through a cooling circuit formed in the turbine blade. The cooling circuit typically consists of a series of connected cooling passages that form serpentine paths, which increase the cooling effectiveness by extending the length of the air flow path.
One exemplary cooling system is multi-walled and includes independent cooling circuits for surfaces of a blade, such as pressure and suction side surfaces, to thereby control specific heat load distributions thereon. The walls form intricate passages through which the cooling air flows to feed serpentine thin outer wall passages that incorporate pin fins, turbulators, turning vanes, and other structures therein. Although the cooling system operates adequately to cool most of the blade's pressure and suction side surfaces, it has been found that some portions of the blade may not be sufficiently cooled. Specifically, in some instances when a blade tip is exposed to extreme heat environments, the tip may oxidize and, thus, may become prematurely worn.
Hence, there is a need for an improved cooling system that is capable of cooling a blade tip in extreme heat environments without allowing the blade to become prematurely worn. Additionally, it would be desirable for the system to be designed such that the blade may be manufactured relatively easily and inexpensively.